This invention relates generally to electronic film processing, and more particularly to a method and system for using calibration patches in electronic film processing.
Conventional color photographic film generally contains three superimposed color sensing layers. Each layer contains a light sensitive material, typically silver halide, that is spectrally sensitive to a specific portion of the visible light spectrum. In general, the top layer responds primarily to light of short wavelength (blue light), the middle layer responds primarily to light of medium wavelength (green light) and the bottom layer responds to light of long wavelength (red light). When film with these types of spectral sensitivities is exposed to visible light, each spot on the film records the intensity of blue, green and red light incident on that location of the film. This film record of incident light referred to as the latent image.
In conventional color photographic development systems, the exposed film is chemically processed to produce color dyes in the three layers with color densities directly proportional to the blue, green and red light intensities recorded as the latent image. Conventional chemical film processing involves the application of a number of processing solutions to the film to produce the color dyes. A developer solution is first applied to the exposed film. In a chemical reaction, the developer solution interacts with the silver halide and couplers in the film to produce elemental silver particles and a respective color dye. The development process is halted at the proper exposure by rinsing the developer solution off the film or a stop solution to the film. A fixing solution is then applied to the film to convert the unexposed silver halide to elemental silver. A bleaching solution is then applied to the film to rinse away the elemental silver and leave the color dyes in each layer. Additional processing solutions can be applied to the film as required to preserve the film. The film is then dried and forms a conventional film negative. Through a conventional printing process, the film negative can be used to produce positive prints of the film negative. The film negative can also be electronically scanned to produce a digital image.
Image enhancement has been the subject of a large body of film processing technology. In particular, color correction is a specific area of image enhancement that is particularly problematic. One difficulty with color correction is trying to correct colors that are incorrect without changing the true colors of the pictured scene.
Briefly summarized, the present invention provides a method for using a calibration patch to electronically process exposed film. In one application, the film is exposed to a calibration light source that creates a reference patch. Developer solution is then applied to the film. The film is then electronically scanned without removing the developer solution to produce an electronic image and an electronic reference image. The electronic reference image is then used to calculate processing parameters for the electronic image. In a particular application, the electronic scanning process comprises electronically scanning the silver metal particles in the film. In another application, the electronic scanning process comprises electronically scanning the dyes in the film. In yet another application, the electronic scanning process comprises a combination of the above.
In another application of the present invention, a method for using a calibration patch in a electronic film processing system is provided. In this application, an unexposed area of the film is exposed to a calibration signal to create a reference patch. The film is then developed to form scene images composed of silver metal particles. Signals corresponding to digital representations of scans of the scene image and the reference patch are generated. Image processing parameters from the signals associated with the reference patch are calculated and used in processing the signals of the digital representations corresponding to the scene image. The image processing parameters then produce initial color values which more accurately reflect the original scene and which are pleasing to the eye.
The invention also provides an improved scanning device used to process a developed scene image on a film according to the present invention. The scanning device comprises a number of optic sensors, an electromagnetic energy source and computer processor. The optic sensors generate digital representations of the scene image and a reference patch image. The computer processor uses the digital representations to calculate image processing parameters based on the reference patch to produce improved color values for the digital representations of the scene image.
The various features and characteristics of the present invention will become more apparent when taken in conjunction with the drawings and the following description wherein like referenced numerals represent like parts.